According to a study spanning across nine European countries, researchers have found that married couples on average eat better than singles, but weigh significantly more and do less sport.

They found that married men were more likely than single men to buy organic and fair trade food. "Men in long-term relationships are likely to eat more consciously and, in turn, probably more healthily," said lead author Jutta Mata, assistant professor of health psychology at University of Basel.

But it does not mean that they are generally healthier. The study showed that married men do less sport than singles. The team compared the relationship between marital status and body mass index (BMI).A high body mass index can be a risk factor for chronic illnesses such as diabetes or cardiovascular disease.

The team of researchers drew on representative cross-sectional data from 10,226 respondents in Austria, France, Germany, Italy, the Netherlands, Poland, Russia, Spain, and Britain. Results from all nine countries showed that couples have a higher BMI than singles - whether men or women.

"Social factors can impact health and in this case, the institution of marriage and certain changes in behaviour within that context are directly related to nutrition and body weight," said Ralph Hertwig from the Max Planck Institute for Human Development in Berlin.

The results were published in the journal Social Science and Medicine.